1. Field of the Invention
The present invention relates to novel fluorine-containing cellulose derivatives, which can be used for fibers, moldings, films, semipermeable membranes, coatings or the like.
2. Description of the Prior Art
Cellulose acetate, one of the cellulose derivatives having many practically useful properties such as good molding characteristic, good solubility in solvents, good film-forming ability and good fiber-forming ability, is well utilized for fibers, moldings, films, semipermeable membranes and coatings. It is the same with cellulose acetate propionate, cellulose acetate butyrate or the like, which correspond to cellulose acetate whose acetyl groups are partially replaced by propionyl group, butyryl group or the like. These cellulose derivatives, however, have defects for specific use, which result from their highly hydrophilic property.
The most effective means for increasing hydrophobic property of a substance is to bond the substance with fluorine atoms or a fluorine-containing compound. However, reagents for introducing fluorine are generally too strong in reactivity and too difficult to deal with, and so it is not easy to introduce fluorine into the starting substance without losing characteristic properties thereof.
Recently, it has been found that hexafluoropropylene oxide (hereinafter abbreviated as HFFO) and its oligomer (hereinafter abbreviated as HFPO oligomer) are effective reagents for introducing fluorine into organic compounds.
The HFPO and HFPO oligomer are relatively easy to deal with and they are strong nucleophilic reagents. When cellulose derivatives were treated with them they reacted with hydroxyl groups of the cellulose derivatives to form ester linkages. Thus, fluorine could be introduced into cellulose derivatives by the reaction with them.